In the maker model export, the released date and the created date are in the form of a number of milliseconds since the 01-01-1970 12:00am Epoch in UTC time-zone.

In order to convert in excel a date format YYYY to a UNiX epoch number of millisecond for all model,
I have used the following formula:

epochdate = (DateValue(YYYY) - 25569) * 86400 * 1000

Note: This formula also works for model with date prior to 1970.

You can also found help to perform this conversion in different programming language using the following website
https://currentmillis.com/

Further help can be found in the Connector 1.13 release video at https://youtu.be/PQ6osVe57uw